Airlines changing rules for emotional support animals

(CNN) -- Millions of people will be flying in the coming weeks to celebrate the holidays with friends and loved ones. Some of those people will be bringing a service or support animal with them. and if that's you, make sure you know the rules.

Due to complaints from other passengers, along with incidents documented by crew members, airlines have made changes to their support animal policies.

Many major airlines will now only accept dogs or cats as service or emotional support animals. Southwest Airlines also accepts miniature horses. However, Delta Airlines has announced that starting December 18th, puppies and kittens, younger than four months old, will not be allowed onboard as service or support animals.

Additionally, emotional support animals will be banned from Delta flights longer than eight hours. All airlines require documentation stating that your animal is specially trained to help you with an approved medical condition, outlined by those airlines. Some also require up to date vaccination records from their vet.

As always, make sure you check with your individual airline ahead of time to find out what they require.